The light emitting diode (LED) array microscope enables various multi-contrast imaging such as bright-field, dark- field and differential phase-contrast (DPC) by various illumination patterns without any expensive optical components. We built LED array microscopic system that enables us to obtain multi-contrast images with a smartphone camera. We demonstrate that a smartphone-based LED array microscope can acquire bright field, dark field, and DPC of cell by changing the numerical apertures of objective lenses.